The thermal stability of packaging compositions such as underfill materials or other organic encapsulation molding compounds, is important in reducing the warpage of chip packages. Desirable materials have properties such as high thermal stability, low shrinkage, a favorable coefficient of thermal expansion (CTE), and other qualities such as a low moisture uptake.
In chip packaging technology, the die is often bond-strengthened to the mounting substrate with an organic material that is flowed into contact with the die and the mounting substrate. In flip-chip processing, the organic material flows between the die active surface and the mounting substrate, thus strengthening the bond therebetween, while protecting the electrical contacts.
Some of the organic material invariably flows beyond the footprint of the die and onto the mounting substrate at the margins of the die. The extent of this organic material flow, restricts the proximity of electrical contacts for passive components that are to be placed near the die, because the organic material can foul their contacts.